Advances in technology have resulted in smaller and more powerful computing devices. For example, there currently exist a variety of portable personal computing devices, including wireless computing devices, such as portable wireless telephones, personal digital assistants (PDAs), and paging devices that are small, lightweight, and easily carried by users. More specifically, portable wireless telephones, such as cellular telephones and Internet Protocol (IP) telephones, can communicate voice and data packets over wireless networks. Further, many such wireless telephones include other types of devices that are incorporated therein. For example, wireless telephones can also include a digital still camera, a digital video camera, a digital recorder, and an audio file player. Also, such wireless telephones can process executable instructions, including software applications, such as a web browser application, that can be used to access the Internet. As such, these wireless telephones can include significant computing capabilities.
Such computing devices may include circuits (e.g., circuits included in a semiconductor device) that are susceptible to damage from an electrostatic discharge (ESD) event (such as during fabrication, packaging, or handling of the device). For example, a current caused by the ESD event may damage or destroy gate oxide, metallization, or junctions of electronic components. Damage caused by the ESD event may reduce manufacturing yields or cause operational failures of the electronic components and devices. Resistor-capacitor (RC) ESD clamps are designed to respond to ESD voltage transients. The RC ESD clamp is configured to be triggered (e.g., activated) to conduct a current between a power supply (e.g., a conductor, a line, or a “rail” that may be coupled to a power source to provide power to an unpowered circuit) and ground in response to an ESD voltage between the power supply and the ground. The RC ESD clamp is configured to conduct the current from the power supply to the ground for a time period on the order of a few microseconds (μs) during an ESD event.
During a typical (i.e., a non-ESD) power-up of a power source coupled to the power supply, the RC ESD clamp is not triggered. A power source may have a relatively long power-up time (e.g., on the order of 10 μs or greater), such as due to charging of a large bypass capacitor, that is longer than the time period of the ESD event. However, increasing performance demands of computer devices have created a need for power sources having a shorter power-up time than the typical power-up time. For example, many wireless telephones power down components (e.g. circuits or processors) when not in use (e.g., enter a standby mode or a power-down mode). It may be desirable for a wireless telephone to have a fast power-up when returning to a powered mode to increase performance.
A fast power-up (e.g., a power-up time that is shorter than a typical power-up time) may cause the RC ESD clamp to momentarily trigger and conduct current between the power supply and the ground, thus encumbering the fast power-up of the power source. For example, the fast power-up of the power source may be part of a power-up sequence associated with the integrated circuit including the RC ESD clamp. Because RC ESD clamps are configured so that large amounts of current (e.g., several amps) may be conducted during the ESD event, triggering the RC ESD clamp during a non-ESD power-up results in increased power consumption, an increased delay in the power-up of the power source, and possible damage to the RC clamp and other circuit elements since energy associated with the power-up may be much greater than energy during an ESD discharge.